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Nikon's New 300mm f/4 Looks Impressive
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<blockquote data-quote="Bengt Nyman" data-source="post: 458481" data-attributes="member: 13692"><p>I agree, it appears form the article that the PDAF described is simply not designed to benefit from light angles beyond that of f/2.8.</p><p>It is also suggested that the speed of the PDAF does suffer when the light level is compromised requiring a longer time for light integration to secure a signal with low enough noise.</p><p>Similarly, a lens which can not produce f/2.8 light angles will reduce the light available to a PDAF system designed for f/2.8, possibly explaining the reduced PDAF speed and performance when using TCs.</p><p>I also conclude, however, that a lens with a TC and a certain effective aperture should produce an AF performance similar to any other lens with the same effective aperture, and possibly totally loosing the ability to autofocus a lens, or a lens+TC, with an effective aperture beyond f/8.</p><p></p><p>Good to know, thank you.</p></blockquote><p></p>
[QUOTE="Bengt Nyman, post: 458481, member: 13692"] I agree, it appears form the article that the PDAF described is simply not designed to benefit from light angles beyond that of f/2.8. It is also suggested that the speed of the PDAF does suffer when the light level is compromised requiring a longer time for light integration to secure a signal with low enough noise. Similarly, a lens which can not produce f/2.8 light angles will reduce the light available to a PDAF system designed for f/2.8, possibly explaining the reduced PDAF speed and performance when using TCs. I also conclude, however, that a lens with a TC and a certain effective aperture should produce an AF performance similar to any other lens with the same effective aperture, and possibly totally loosing the ability to autofocus a lens, or a lens+TC, with an effective aperture beyond f/8. Good to know, thank you. [/QUOTE]
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Nikon's New 300mm f/4 Looks Impressive
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